Fluorine

Fluorine

Fluorine is a chemical element that in pure form occurs as a dimer of two fluorine atoms, F2. The fluorine atom has the ground state electron configuration 1s22s22p5. There is only one stable, naturally occurring isotope of fluorine: 19F. However, the radioactive isotopes 17F, 18F, and 20F are known. The inclusion of the isotope 18F (half-life 110 minutes) in bioorganic molecules is an important noninvasive technique used in the study of living tissue by positron emission tomography.

Fluorine is the most electronegative element. It is the lightest and most reactive element in the halogen family. Fluorine is a poisonous, corrosive, pale yellow gas with an acrid odor. It is the most powerful oxidizing agent known. The low F–F bond energy and the high energy of bonds between fluorine and other elements combine to make reactions of fluorine exothermic.

Elemental fluorine was first prepared by Henri Moissan in France in 1886 via the electrolysis of anhydrous hydrogen fluoride in the presence of potassium fluoride. Fluorine forms compounds with all of the elements except helium, neon, and argon. In nature, fluorine is primarily found in the minerals fluorospar (CaF2), cryolite (Na3AlF6), and fluoroapatite (CaF2·3Ca3(PO4)2), together comprising 0.065 percent of Earth's crust (making fluorine the thirteenth most abundant element). These minerals are widely used as electrolytes in the preparation of aluminum, as fluxes in the metallurgy of iron, and as additives in ceramics.

Other important inorganic compounds of fluorine include uranium hexafluoride, UF6, a volatile substance that was used to separate 238U from the fissionable235U by gaseous diffusion in the Manhattan Project . Sodium fluoride, NaF, is often added to drinking water and to toothpaste in order to reduce the incidence of tooth decay.

When hydrogen is replaced by fluorine in organic compounds, the properties of the compounds are substantially altered. The new compounds have increased chemical, thermal, and oxidative stability. Low molecular weightchlorofluorocarbons , known as Freons, are nonflammable, dense, nontoxic compounds particularly useful as refrigerants and blowing agents. Substitutes for these ozone-depleting compounds are being developed.

Teflon (polytetrafluoroethylene) is a chemically inert polymer used to create nonstick frying pans. Polytetrafluoroethylene can be modified to form a coating, Gore-Tex, which allows the passage of water vapor, but not liquid water, and is used in many articles of clothing. Polymeric perfluorinated ethers are widely used as high performance oils and lubricants.

The introduction of one to three fluorine atoms to large organic molecules, such as steroids, has been shown to modify the biological activity of these molecules. Many of these fluorine-containing compounds that are useful as pharmaceutical agents have been prepared. The compound 5-fluorouracil is a widely used anticancer agent. Prozac (containing fluorine) is a well-known antidepressant drug. In addition, agrochemists have developed many herbicides (e.g., trifluralin), insecticides (e.g., diflubenzuron), and fungicides (e.g., flutriafol) that incorporate fluorine. Fluorinated dyestuffs and fluorinated liquid crystals have also found commercial use.

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fluorine

fluorine (symbol F) Gaseous toxic element of the halogen group (elements in group VII of the periodic table), isolated in 1886 by Henri Moissan. Chief sources are fluorspar and cryolite. The pale yellow element, obtained by electrolysis, is the most electronegative element and the most reactive nonmetallic element. It is in fluoride in drinking water and is used in making fluorocarbons and in extracting uranium. Properties: at.no. 9; r.a.m. 19; m.p. −219.6°C (−363.3°F); b.p. −188.1°C (−306.6°F); single isotope F19.

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fluorine

The Columbia Encyclopedia, 6th ed.

Copyright The Columbia University Press

fluorine (flōō´ərēn, –rĬn), gaseous chemical element; symbol F; at. no. 9; at. wt. 18.9984; m.p. -219.6°C; b.p. -188.14°C; density 1.696 grams per liter at STP; valence -1. Fluorine is a yellowish, poisonous, highly corrosive gas. It is the most chemically active nonmetallic element and is the most electronegative of all the elements. It is a member of Group 17 (the halogens) of the periodic table.

Fluorine readily displaces the other halogens from their salts. It combines spontaneously with most other elements—exceptions are chlorine, nitrogen, oxygen, and the so-called inert gases (helium, neon, argon, krypton, xenon, and radon), but it even combines with most of these when heated. Fluorine reacts with most inorganic and organic compounds. With hydrogen it forms hydrogen fluoride gas, whose water solution is called hydrofluoric acid.

Because of its extreme reactivity, fluorine does not occur uncombined in nature. Fluorine gas is produced commercially by electrolysis of a solution of hydrogen fluoride containing potassium hydrogen fluoride. The mineral fluorite, or fluorspar (calcium fluoride), is the chief commercial source. Cryolite and apatite are other important natural compounds.

The importance of fluorine lies largely in its compounds. Fluorite is used as a flux in refining iron; cryolite serves as the electrolyte in the production of aluminum. Compounds of fluorine are also used in the ceramic and glass industries; hydrofluoric acid is used to etch glass and in the manufacture of light bulbs. The addition of one part per million of soluble fluorides to public water supplies has reduced the incidence of tooth decay in many communities, but water with naturally occurring levels as low as four parts per million can damage teeth and bones. In even larger amounts fluorine and fluoride compounds are poisonous. Sodium fluoride is employed as an insecticide.

Halocarbons (compounds of carbon, fluorine, chlorine, and hydrogen) are used extensively in refrigeration and air-conditioning systems. They were widely used as aerosol propellants; but, since they cause depletion of the ozone layer, government restrictions have nearly abolished such use. The linking of fluorine and carbon has created some of the most chemically inert compounds known. Fluorocarbons such as Teflon have found extensive use as lubricants and bearing materials because of their low friction. Because of their inertness and heat resistance they may be used, for example, as a coating on cooking ware. Because they are not wetted by water or oils, they are sometimes used to add antisoil properties to textiles.

The use of fluorite as a flux was described in 1529 by Georgius Agricola. Many early chemists experimented with hydrogen fluoride gas, among them Scheele, Davy, Lavoisier, and Gay-Lussac. Fluorine gas was first prepared in 1886 by Henri Moissan after nearly three quarters of a century of effort. There was no commercial production of fluorine before World War II, when the use of the gas in a process for refining uranium ores prompted its manufacture.

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fluorine

fluor·ine
/ ˈfloŏrˌēn; flôr-/
•
n.
the chemical element of atomic number 9, a poisonous pale yellow gas of the halogen series. It is the most reactive of all the elements, causing severe burns on contact with skin.
(Symbol: F)

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